Diagnostic accuracy of the Barr and Blethyn radiological scoring systems for childhood constipation assessed using colonic transit time as the gold standard.

BACKGROUND: Constipation is a common childhood symptom and abdominal radiography is advocated in diagnosis and management.
OBJECTIVE: To assess the reproducibility and diagnostic accuracy of the Barr and Blethyn systems for quantifying constipation on abdominal radiographs in children.
MATERIALS AND METHODS: Radiographs were scored by three observers of increasing radiological experience (student, junior doctor, consultant). Abdominal radiographs produced during measurement of colonic transit time (CTT) were classified as constipated or normal based on the value of the transit time, and were scored using both systems by observers blinded to the CTT. Abdominal radiographs obtained in children for reasons other than constipation were classed as normal and similarly scored. Reproducibility was measured using the kappa statistic. Diagnostic accuracy was measured using the area under the curve (AUC) for the receiver operator characteristic (ROC) curve.
RESULTS: Using either system, scores were higher for constipated children (P<0.01). The consultant produced higher scores than the other observers (P<0.01). Interobserver reproducibility was moderate with the best kappa value only 0.48. The best correlation between score and CTT was 0.51 (junior doctor scores). Diagnostic accuracy of the scores was only moderate, with the largest AUC for a ROC curve of 0.84 for the consultant using the Barr score.
CONCLUSIONS: Scoring of abdominal radiographs in the assessment of childhood constipation should be abandoned because it is dependent on the experience of the observer, is poorly reproducible, and does not accurately discriminate between constipated children and children without constipation.